Glutaraldehyde as a microbiological slime inhibitor in micro-irrigation systems

ABSTRACT

A method of preventing the formation of microbiological deposits in the water delivery systems of micro-irrigation systems which have in addition to water delivery systems, a water filtration system, a pump and a water distribution system. This method comprises cleaning the micro-irrigation system to remove existing microbiological deposits thereby providing a clean distribution and delivery system, and then continuously treating the water fed to the delivery system with a few ppm of glutaraldehyde to maintain cleanliness. The invention is particularly effective in controlling microbiological deposits which are either slimes or algae or mixtures thereof.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The prevention of microbiological deposits in micro-irrigationsystems.

[0003] 2. Description of the Prior Art

[0004] Micro-irrigation systems are utilized extensively for growingcrops throughout the world. These systems provide a very uniformdistribution of water directly to the irrigated crop in the most costeffective manner. Micro-irrigation is replacing the older methods ofirrigation such as flood, furrow, ditch, and overhead sprinklerirrigation because of the ever increasing shortage of water supplies andincreased cost of these water supplies. Since micro-irrigationdramatically lowers the cost of the irrigation process, almost everygrower is driven to use this method of irrigation to survive theeconomic pressures of today's world.

[0005] Micro-irrigation systems typically include the following:

[0006] 1. A source of water, which is usually a reservoir, canal, streamor well.

[0007] 2. A pump to deliver the water.

[0008] 3. A filtration system for removing particulate or other debris.

[0009] 4. A distribution system, which consists of an extensive networkof pipes and valves.

[0010] 5. A delivery system, which is the heart of the micro-irrigationsystem. There are many types of delivery systems that are used toaccomplish the accurate delivery of the water. Among these deliverysystems are: in-line emitters (both pressure compensated andnon-pressure compensated); drip tape (both pressure compensated andnon-pressure compensated); external emitters (both pressure compensatedand non-pressure compensated); and micro-sprinklers (both pressurecompensated and non-pressure compensated).

[0011] The major problem that results during the use of themicro-irrigation system occurs because of the unique design of thesevery effective water delivery systems. The problem arises because thewater sources are usually laden with microorganisms. In the case ofsurface waters, such as reservoirs, canals or streams, the majorbiological problem is in the form of algae. In the case of wells, themajor problems are slimes, which contain iron-bacteria andmanganese-bacteria. These bacteria convert water soluble species of ironand manganese compounds into insoluble forms thereof.

[0012] The suppliers of micro-irrigation systems have tried to eliminatethese microbiological problems by installing filtration systems. Whilethese filtration systems do remove some debris and particulates, but dueto the very large flow rates of water (typically 1000 gallons perminute), these sand-media, screen, and synthetic-media filters are notcompletely efficient for removing all of these biological contaminants.Although significant amounts of algae, slime and particulate compoundsof iron and manganese are removed via filtration, there is still a smallamount of these materials that are passed through the filtration system.In the case of algae and slimes, both of these biological entities aresimply extruded through the filters. With iron and manganese bacteriamost of the insoluble compounds of iron and manganese are removed by thefilter. However, there is always some soluble iron and manganese thatcannot be filtered out and the bacteria are too small in size to bestopped by the filter. It is these unforeseen and unexpected low levelsof biological contaminants that this invention addresses and eliminates.

[0013] In ordinary water delivery systems these low levels of biologicalcontaminants would not be a problem. However, these micro-irrigationsystems quite unexpectedly lend themselves to an exacerbation of thesebiological problems. As mentioned previously, the manufacturers of thesemicro-irrigation systems provide filtration that should alleviate thepotential microbiological problems. The unexpected problem arises inthat even very low levels of microbiological contaminants pass throughthe filtration system. These contaminants are then subjected to anenvironment at the end of the micro-irrigation system that leads to an“incubator” for microbial growth that is unique to micro-irrigation andis not present in other water delivery systems. This “incubator” effecthappens in the delivery system. The delivery system precisely controlsthe water delivery to each individual plant in the crop that is beingirrigated by an emitter or micro-sprinkler. These devices, as well asthe rest of the plastic that comprises the drip pipe, tape or tubing, ismade of a black plastic, such as polyethylene or PVC or other plasticthat is impregnated with a black colorant. The manufacturers of thesystem have incorporated the black colorant into the plastic for UVstabilization of the plastic. Although this colorant does an excellentjob at prolonging the life of the plastic components, the black plasticabsorbs sunlight and is warmed during the day, providing perfecttemperatures for the “incubator” effect. The other unexpected problemresults because of the design for precise water control to each plantthat is being irrigated. The emitter or micro-sprinkler that isdelivering water to an individual plant is designed with either a softplastic diaphragm and/or a torturous pathway for restriction of waterflow. In either case, the device has a section that restricts the waterflow. It is because of this unique design that it delivers a preciserate of water to the irrigated plant. As a result of the design andconfiguration of all commercial irrigation delivery devices, smallamounts of light can penetrate the orifice of the device.

[0014] In the case of algae, this light level is sufficient to allow forthe growth of the very low levels of algae that have passed through thefiltration system. The worst-case scenario occurs with a light sourceand the warm temperature of the black components. With both light andheat the algae proliferate on the diaphragm of the emitter and/or in thetorturous pathway in the device. When this happens, depending on thedesign of the device, the device plugs or “sticks” open. In either case,this situation causes severe problems with the operation of themicro-irrigation system. Plugging results in less water being deliveredto the plant, and pressure builds up in the overall irrigation system asmore and more devices plug. This causes poor crop development, increasedcost resulting from over irrigating to get enough water distributedthroughout the field, and increased energy costs to operate the systemat higher pressures. When a device flows open an even worse scenariodevelops. In this case, when many devices “stick” open many portions ofthe field are over irrigated. At first this would not seem to be a majorproblem. However, if some parts of the field have excess waterdelivered, other portions will be under-irrigated. This commonly occursbecause irrigation systems have been designed to deliver a maximumamount of water. If too much water flows out of one section,insufficient capacity is left for the remainder of the field. This isparticularly a problem in elevated or rolling terrains, where the lowerparts of the field are over irrigated, and the upper elevations receiveno water.

[0015] In the case of slimes or iron/manganese bacteria, light is notrequired, but a similar problem still results. Many crops are notirrigated every day. On the off days, this same “incubator” effect is inplace to provide an ideal temperature for growth of the slimes andiron/manganese bacteria. When bacteria or slimes are present there isanother unexpected problem that happens as a result of the emitter ormicro-sprinkler design. When the system is off there is no waterpressure on the irrigation system and the emitters or micro-sprinklersare “open to the environment”. When the irrigation system isdepressurized the delivery device is open to the environment. Inpressure-compensating delivery devices this occurs when the diaphragmrelaxes and opens to the atmosphere. In the case of nonpressure-compensating delivery devices, the tortuous path of the emittersimply is open to the atmosphere when no water is flowing. Again, ineither case, air exchange can take place between the water deliverydevice and the environment. When this happens the damp, warm deliverydevice is now under aerobic conditions, where slimes and bacteria canproliferate, and plug the device or cause the device to “stick” open anddeliver too much water on the next irrigation cycle.

SUMMARY OF THE INVENTION

[0016] A method of preventing the formation of microbiological depositsin the water delivery systems of micro-irrigation systems which have inaddition to water delivery systems have a water filtration system, apump and a water distribution system. The method comprises cleaning themicro-irrigation system to remove existing microbiological depositsthereby providing a clean distribution and delivery system, and thentreating, preferably continuously, the water fed to the delivery systemwith a few ppm of glutaraldehyde. The term, “cleaning” as used hereinand in the claims includes new start-up systems that have not previouslybeen used to delivery irrigation water.

[0017] In a preferred embodiment the glutaraldehyde is continuously fedto the delivery system and is added after the filtration system. Themicrobiological deposits are most commonly bacterial slimes, algae ormixed bacterial slimes and algae. Most often these slimes have as aportion of their makeup iron and magnesium bacteria which convertsoluble forms or iron and manganese into insoluble forms of thesemetals.

[0018] One of the important aspects of the invention resides in the factthat the glutaraldehyde maintains these micro-irrigation systems in aclean condition using a relatively low dosages thereof. Specifically,the glutaraldehyde may be applied at a dosage ranging between 0.1-10ppm. In a preferred embodiment the dosage may range between 0.5-5 ppm.Typical of the low dosages that produce excellent results are thoseranging between 1-5 ppm.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The laboratory test study was conducted by developing anaccelerated method by which various dosages of glutaraldehyde could beevaluated. Since it may take an entire growing season to accumulateenough biological deposit in a delivery device to cause plugging or a“stuck open” condition, a laboratory screening study was developed totest the efficacy of various glutaraldehyde dosages under a worse casescenario. To accomplish this screening test, a common emitter used bymany growers was chosen as the test case. This emitter is adiaphragm-type pressure-compensating emitter (Rain Bird). To obtainemitters that already had a build-up of a biological contamination, asite was chosen where the emitters had been known to be malfunctioning.In the case of the Rain Bird emitters, a prelude to plugging is whenthese emitters begin to “spit”, in all directions, instead of justdripping down toward the ground. The “spitting” characteristic made thedetection of potentially problematic emitters easy to identify. Toobtain a good distribution, 100 of these problem emitters were takenfrom the field and put through the screening study.

[0020] To determine if there was a biological deposit built up in theseemitters, five emitters were selected randomly and cut open to observethe biological deposit. Since the water source was a reservoir, thedeposit was mostly algae as determined by visual inspection. The depositwas determined to be of significant quantity in these emitters so as toutilize them in the screening study.

[0021] To obtain a water sample from the source of the water, twofive-gallon samples of the reservoir water were taken after thefiltration system. This water was used for all subsequent laboratorytesting. In between testing periods this water was stored underrefrigerated temperatures to minimize any additional microbiologicalgrowth.

[0022] Since cost is extremely important for the grower, only two dosagelevels were chosen to study. These levels were 1 ppm and 5 ppm activeglutaraldehyde. The test procedure for evaluation was as follows:

[0023] 1. 100 ml of test solution was passed through each tested emitterto ensure the treatment had thoroughly passed through the emitter. Thiswas accomplished by means of a positive displacement pump that pumped ata rate of about 200 ml per 5 minutes.

[0024] 2. For the control, twenty-five such emitters were treated withjust the filtered reservoir water, as indicated in step 1. Alltwenty-five emitters where then placed in a 1 quart Mason jar containing500 ml of the filtered reservoir water. This Mason jar was then placedin the sun for the prescribed period of time.

[0025] 3. For the 1 ppm treatment, twenty-five such emitters weretreated with the filtered reservoir water, as indicated in step 1, towhich was added 1 ppm active glutaraldehyde. All twenty-five emitterswere then placed in a 1-quart Mason jar containing 500 ml of thefiltered reservoir water containing 1 ppm glutaraldehyde. This Mason jarwas then placed in the sun for the prescribed period of time.

[0026] 4. For the 5 ppm treatment twenty-five such emitters were treatedwith filtered reservoir water, as indicated in step 1, to which 5 ppmactive glutaraldehyde was added. All twenty-five emitters were thenplaced in a 1-quart Mason jar containing 500 ml of the filteredreservoir water containing 5 ppm glutaraldehyde. This Mason jar was thenplaced in the sun for the prescribed period of time.

[0027] 5. To test the efficacy, five emitters from steps 2, 3, and 4were removed from the Mason jars at various intervals and treated asdescribed below. To remove any residual treatment and to simulate flowconditions through the emitter, distilled water was passed through eachemitter at a rate of approximately 35 ml per minute for 24 hours. At theend of the 24 hour flush treatment, the emitters were cut open andinspected for any visual biological debris. To ensure the emittersremaining in the Mason jar experienced a fresh treatment, steps 1, 2, 3and 4 were redone on all the remaining emitters.

[0028] 6. The time intervals for evaluation of the control and the twoglutaraldehyde dosage levels were as follows: 0 days, 10 days, 20 days,30 days and 45 days.

[0029] The results of this study can be seen in Table I, Table II, TableIII, Table IV and Table V. TABLE I Time Emitter Dosage Level PeriodNumber (glutaraldehyde) Visual Observation 0 days 1 0 ppm Diaphragmcompletely covered with green deposit. Rating 100% covered. Rating 100%alive. 0 days 2 0 ppm Diaphragm completely covered with green deposit.Rating 105% covered. Rating 100% alive. 0 days 3 0 ppm Diaphragmcompletely covered with green deposit. Rating 100% covered. Rating 100%alive. 0 days 4 0 ppm Diaphragm completely covered with green deposit.Rating 95% covered. Rating 100% alive. 0 days 5 0 ppm Diaphragmcompletely covered with green deposit. Rating 95% covered. Rating 100%alive. 0 days 1 1 ppm Diaphragm completely covered with green deposit.Rating 95% covered. Rating 100% alive. 0 days 2 1 ppm Diaphragmcompletely covered with green deposit. Rating 105% covered. Rating 100%alive. 0 days 3 1 ppm Diaphragm completely covered with green deposit.Rating 105% covered. Rating 100% alive. 0 days 4 1 ppm Diaphragmcompletely covered with green deposit. Rating 100% covered. Rating 100%alive. 0 days 5 1 ppm Diaphragm completely covered with green deposit.Rating 100% covered. Rating 100% alive. 0 days 1 5 ppm Diaphragmcompletely covered with green deposit. Rating 100% covered. Rating 100%alive. 0 days 2 5 ppm Diaphragm completely covered with green deposit.Rating 100% covered. Rating 100% alive. 0 days 3 5 ppm Diaphragmcompletely covered with green deposit. Rating 105% covered. Rating 100%alive. 0 days 4 5 ppm Diaphragm completely covered with green deposit.Rating 105% covered. Rating 100% alive. 0 days 5 5 ppm Diaphragmcompletely covered with green deposit. Rating 100% covered. Rating 100%alive.

[0030] TABLE II Time Emitter Dosage Level Period Number (gluraldehyde)Visual Observation 10 days 1 0 ppm Diaphragm completely covered withgreen deposit. Rating 105% covered. Rating 100% alive. 10 days 2 0 ppmDiaphragm completely covered with green deposit. Rating 105% covered.Rating 100% alive. 10 days 3 0 ppm Diaphragm completely covered withgreen deposit. Rating 100% covered. Rating 100% alive. 10 days 4 0 ppmDiaphragm completely covered with green deposit. Rating 95% covered.Rating 100% alive. 10 days 5 0 ppm Diaphragm completely covered withgreen deposit. Rating 105% covered. Rating 100% alive. 10 days 1 1 ppmDiaphragm mostly covered with brown/green deposit. Rating 85% covered.Rating 80% alive. 10 days 2 1 ppm Diaphragm mostly covered withbrown/green deposit. Rating 90% covered. Rating 80% alive. 10 days 3 1ppm Diaphragm mostly covered with brown/green deposit. Rating 90%covered. Rating 85% alive. 10 days 4 1 ppm Diaphragm mostly covered withbrown/green deposit. Rating 85% covered. Rating 85% alive. 10 days 5 1ppm Diaphragm mostly covered with brown/green deposit. Rating 90%covered. Rating 80% alive. 10 days 1 5 ppm Diaphragm partly covered withbrown deposit. Rating 20% covered. Rating 0% alive. 10 days 2 5 ppmDiaphragm partly covered with brown deposit. Rating 30% covered. Rating0% alive. 10 days 3 5 ppm Diaphragm partly covered with brown deposit.Rating 30% covered. Rating 0% alive. 10 days 4 5 ppm Diaphragm partlycovered with brown deposit. Rating 25% covered. Rating 0% alive. 10 days5 5 ppm Diaphragm partly covered Rating 10% covered. Rating 0% alive.

[0031] TABLE III Time Emitter Dosage Level Period Number(glutaraldehyde) Visual Observation 20 days 1 0 ppm Diaphragm completelycovered with green deposit. Rating 105% covered. Rating 100% alive. 20days 2 0 ppm Diaphragm completely covered with green deposit. Rating100% covered. Rating 100% alive. 20 days 3 0 ppm Diaphragm completelycovered with green deposit. Rating 100% covered. Rating 100% alive. 20days 4 0 ppm Diaphragm completely covered with green deposit. Rating110% covered. Rating 100% alive. 20 days 5 0 ppm Diaphragm completelycovered with green deposit. Rating 100% covered. Rating 100% alive. 20days 1 1 ppm Diaphragm partly covered with brown deposit. Rating 40%covered. Rating 5% alive. 20 days 2 1 ppm Diaphragm partly covered withbrown deposit. Rating 25% covered. Rating 0% alive. 20 days 3 1 ppmDiaphragm partly covered with brown deposit. Rating 25% covered. Rating0% alive. 20 days 4 1 ppm Diaphragm partly covered with brown deposit.Rating 30% covered. Rating 5% alive. 20 days 5 1 ppm Diaphragm partlycovered with brown deposit. Rating 35% covered. Rating 5% alive. 20 days1 5 ppm Diaphragm free of deposits. Rating 0% covered. Rating 0% alive.20 days 2 5 ppm Diaphragm free of deposits. Rating 0% covered. Rating 0%alive. 20 days 3 5 ppm Diaphragm free of deposits. Rating 0% covered.Rating 0% alive. 20 days 4 5 ppm Diaphragm free of deposits. Rating 0%covered. Rating 0% alive. 20 days 5 5 ppm Diaphragm free of deposits.Rating 0% covered. Rating 0% alive.

[0032] TABLE IV Time Emitter Dosage Level Period Number (glutaraldehyde)Visual Observation 30 days 1 0 ppm Diaphragm completely covered withgreen deposit. Rating 100% covered. Rating 100% alive. 30 days 2 0 ppmDiaphragm completely covered with green deposit. Rating 105% covered.Rating 100% alive. 30 days 3 0 ppm Diaphragm completely covered withgreen deposit. Rating 95% covered. Rating 100% alive. 30 days 4 0 ppmDiaphragm completely covered with green deposit. Rating 100% covered.Rating 100% alive. 30 days 5 0 ppm Diaphragm completely covered withgreen deposit. Rating 100% covered. Rating 100% alive. 30 days 1 1 ppmTrace of brown deposit on diaphragm. Rating 5% covered. Rating 0% alive.30 days 2 1 ppm Diaphragm free of deposits. Rating 0% covered. Rating 0%alive. 30 days 3 1 ppm Diaphragm free of deposits. Rating 0% covered.Rating 0% alive. 30 days 4 1 ppm Trace of brown deposit on diaphragm.Rating 10% covered. Rating 0% alive. 30 days 5 1 ppm Trace of browndeposit on diaphragm. Rating 5% covered. Rating 0% alive. 30 days 1 5ppm Diaphragm free of deposits. Rating 0% covered. Rating 0% alive. 30days 2 5 ppm Diaphragm free of deposits. Rating 0% covered. Rating 0%alive. 30 days 3 5 ppm Diaphragm free of deposits. Rating 0% covered.Rating 0% alive. 30 days 4 5 ppm Diaphragm free of deposits. Rating 0%covered. Rating 0% alive. 30 days 5 5 ppm Diaphragm free of deposits.Rating 0% covered. Rating 0% alive.

[0033] TABLE V Time Emitter Dosage Level Period Number (glutaraldehyde)Visual Observation 45 days 1 0 ppm Diaphragm completely covered withgreen deposit. Rating 100% covered. Rating 100% alive. 45 days 2 0 ppmDiaphragm completely covered with green deposit. Rating 100% covered.Rating 100% alive. 45 days 3 0 ppm Diaphragm completely covered withgreen deposit. Rating 105% covered. Rating 100% alive. 45 days 4 0 ppmDiaphragm completely covered with green deposit. Rating 105% covered.Rating 100% alive. 45 days 5 0 ppm Diaphragm completely covered withgreen deposit. Rating 100% covered. Rating 100% alive. 45 days 1 1 ppmDiaphragm free of deposits. Rating 0% covered. Rating 0% alive. 45 days2 1 ppm Diaphragm free of deposits. Rating 0% covered. Rating 0% alive.45 days 3 1 ppm Diaphragm free of deposits. Rating 0% covered. Rating 0%alive. 45 days 4 1 ppm Diaphragm free of deposits. Rating 0% covered.Rating 0% alive. 45 days 5 1 ppm Diaphragm free of deposits. Rating 0%covered. Rating 0% alive. 45 days 1 5 ppm Diaphragm free of deposits.Rating 0% covered. Rating 0% alive. 45 days 2 5 ppm Diaphragm free ofdeposits. Rating 0% covered. Rating 0% alive. 45 days 3 5 ppm Diaphragmfree of deposits. Rating 0% covered. Rating 0% alive. 45 days 4 5 ppmDiaphragm free of deposits. Rating 0% covered. Rating 0% alive. 45 days5 5 ppm Diaphragm free of deposits. Rating 0% covered. Rating 0% alive.

[0034] This invention overcomes these unexpected biological problemsthat occur in micro-irrigation systems by treating the irrigation waterwith very low levels of glutaraldehyde. What makes this treatmentprocess unique is that very low levels of glutaraldehyde can be dosedbecause the bulk of the biological load in normal ground and/or surfacewaters are removed, via the filtration process. A small maintenancelevel, typically lppm glutaraldehyde is added to all irrigation water.As a result, this threshold level of glutaraldehyde maintains a cleandelivery device so that none of the aforementioned problems arise. Theresult is a micro-irrigation system that remains free of microbialgrowth in the delivery devices and that is capable of delivering waterto each plant precisely, and according to the manufacturer'sspecifications.

[0035] The micro-irrigation systems may be cleaned prior to theinitiation of the low levels of glutaraldehyde using known methods forremoving scale and microbiological deposits. For instance, suchtechniques as mild acid cleaning may be used. Preferred is the use ofbiocides such as chlorine or mixtures of chlorine and bromine andglutaraldehyde at high dosages, e.g. 20 ppm or more for several days toprovide a clean deposit-free system.

[0036] The invention is applicable for treating micro-irrigation systemsutilizing such mechanical delivery systems as drip hoses with in-lineemitters, drip hose with external emitters, drip tapes andmicro-sprinklers. Any of the above type systems may be either pressureor non-pressure compensated type systems.

[0037] Finally, it should be noted that in addition to being effectiveat extremely low dosages, glutaraldehyde is a safe biocide which isimportant since many well known yet effective biocides such asformaldehyde are not capable of being used in micro-irrigationapplications due to local and federal laws.

We claim:
 1. A method of preventing the formation of microbiologicaldeposits in the water delivery systems of micro-irrigation systems whichhave in addition to a water delivery system, a water filtration system,a pump and a water distribution system which comprises the steps of: (a)cleaning the micro-irrigation system to remove existing microbiologicaldeposits thereby providing a clean distribution and delivery system, andthen; (b) treating the water fed to the delivery system with a few ppmof glutaraldehyde.
 2. The method of claim 1 where the glutaraldehyde iscontinuously fed to the delivery system.
 3. The method of claim 2 wherethe glutaraldehyde is added after the water filtration system.
 4. Themethod of claim 1 where the microbiological deposits are slimes.
 5. Themethod of claim 4 where the slimes contain iron and manganese bacteria.6. The method of claim 1 where the microbiological deposits are algae.7. The method of claim 1 where the microbiological deposits are amixture of slimes and algae.
 8. The method of claim 7 where the mixtureof slimes and algae contain iron and manganese bacteria.
 9. The methodof claim 1 where the glutaraldehyde is fed at a dosage ranging between0.1-10 ppm.
 10. The method of claim 1 where the glutaraldehyde is fed ata dosage ranging between 0.5-5 ppm.
 11. The method of claim 1 where theglutaraldehyde is fed at a dosage ranging between 1-5 ppm.